Mix all ingredients in a small bowl.
Rub brisket all over with spice rub. Cover and chill for at least 2 hours or overnight. Let stand at room temperature for 1 hour before continuing.
Preheat oven to 165 degrees. Heat 1 tablespoon oil in a large wide pot over high heat. Add brisket, fat side down. Cook undisturbed until well browned, 5-6 minutes. Turn brisket over and cook until browned, about 3 minutes. Using tongs, transfer to a plate.
Reduce heat to medium and add remaining 1 tablespoon oil.
Add onion and garlic. Cook, stirring occasionally, until onion is slightly golden, about 5 minutes.
Add broth and all remaining ingredients. Bring liquid to a simmer. Return brisket to pot. Cover and transfer to oven.
Braise until brisket is very tender to the touch but still holds its shape, about 4 1/2 hours.
Using a large spatula, transfer brisket, fat side up, to a large plate. Strain braising liquid into a large bowl. Return liquid to pot, bring to a simmer, and cook until reduced to 2 cups, about 15 minutes.
Score fat side of brisket by cutting a crosshatch pattern of 1/4″-deep slits spaced 1/2″ apart. Return brisket, fat side up, to pot with reduced braising liquid.
DO AHEAD: Brisket can be made 2 days ahead. Return brisket to pot, cover, and chill. Bring to a simmer and rewarm brisket before proceeding.
Transfer 1/4 cup braising liquid to a blender. Add jam and bourbon and purée until smooth. Season with salt and pepper.
Preheat boiler. Spread 3-4 tablespoons glaze on top of brisket with the back of a spoon. boil brisket in pot until browned and glazed, watching carefully to prevent burning, 4-5 minutes.